A conventional crawler device for a crawler vehicle is provided with right and left crawler links for fastening a multiplicity of crawler plates arranged in a longitudinal direction of a crawler.
The multiplicity of arranged right and left crawler links are overlapped and connected by press fitting a pin and a stationary bush. Then, it has been structured such as to mesh teeth of a drive wheel with an outer diameter portion of the stationary bush so as to rotate, however, since the outer diameter portion of the stationary bush is worn away, a crawler device in which a rotating bush is outwardly fitted to the stationary bush has been developed in recent days.
As a prior art of the crawler device using the rotating bush, there is, for example, Japanese Unexamined PCT Publication No. 6-504747. The contents thereof is structured such that stationary bushes 110 and 110 are respectively press fitted to right and left crawler links 80a and 80b, as shown in FIG. 9.
A rotating bush 120 is provided in a center portion between the left stationary bush 110 and the right stationary bush 110, and the structure is made such as to be separated into three portions.
The center rotating bush 120 meshed with the teeth of the drive wheel (not shown) can rotate around a pin 100. A portion between an inner cylinder surface of the center rotating bush 120 and an outer diameter portion of the pin 100 are lubricated by an oil, and each of seals 150 and 150 is provided between right and left end surfaces of the rotating bush 120 and each of the stationary bushes 110 and 110. Each of seals 140 and 140 is provided outside each of the stationary bushes 110 and 110. Oil grooves 101 and 102 are provided in an inner portion of the pin 100.
However, in accordance with the technique described in this publication, since each of the seals 150 and 150 is arranged in both end portions of the rotating bush 120, it is unavoidable to reduce a length or a volume of press fitting between the right and left crawler links 80a and 80b and each of the stationary bushes 110 and 110. Further, since the right and left crawler links 80a and 80b are press fitted and fixed by two stationary bushes 110 and 110 not by single one, there is no bush for combining and connecting between the right crawler link 80a and the left crawler link 80b, so that a torsional rigidity between the right and left crawler links 80a and 80b is significantly reduced. Accordingly, there are problems that a holding force due to a press fitting is insufficient against an external force during an operation, a clearance (an end play) of each of seals 140 and 150 at an initial time of assembly is expanded and a sealed lubricating oil is leaked from each of the seals 140 and 150.
Further, a lubrication between the pin 100 and the rotating bush 120 is insufficient, so that there is a problem that they seize and an endurance life is reduced.
Still further, since the right and left crawler links 80a and 80b are twisted due to the external force applied during the operation, there is a problem that the pin 100, each of the stationary bushes 110 and 110, the rotating bushes 120 and the like are worn away, so that a durability of the crawler device is reduced.